Purifying sulphur-containing substances



March 27, 1934. WHITAKER 1,952,482

PURIFYING SULPHUR CONTAINING SUBSTANCES 7 Filed June 28, 1929 &

77757750 0/5 T/ZAHTE INVEyN/TOR 3% M ATTORN EY .S'

Patented Mar. 27, 1934 UNITED STATES PATENT OFFICE mesne assignments, to The Petroleum Proeesses Corporation, Wichita, Kans., a corporation of Kansas Application June 28, 1929, Serial No. 374,527

'7 Claims.

My invention relates to the art of purifying sulphur-containing substances and more particularly, the purification of sulphur-containing mineral oils and oils derived from coal tar.

My invention relates particularly to the purification of distillates derived from'petroleum and coal tar and it is not necessarily limited to the treatment and purification of oils containing sulphur.

My invention also relates to a new and improved purified material in which the sulphur content has been diminished.

One of the objects of my invention is to provide a method for purifying naphtha and gasoline.

Another object of my invention is to provide a method whereby volatile sulphur-containing compounds can be readily eliminated from oils which can be vaporizedwithout injuring the same.

Another object of my invention is to provide a method of purifying vaporized materials by subjecting them either to adsorbing or catalytic action so as to produce a reaction or reactions whereby objectionable sulphur-containing compounds can be transformed into another sulphurcontaining compound or compounds which can be readily removed.

Another object of my invention is to purify an oil from an objectionable sulphur-containing compound or compounds, without adding any additional material to said oil, but producing a reaction or reactionswhereby the objectionable sulphur-containing compound or compounds can be transformed into another sulphur-containing compound or compounds which can be more readily removed.

My invention is particularly useful in treating petroleum or tar distillates such as coal tar distillates, and more particularly gasoline and naphtha which contains from ,11 percent to .50 percent of sulphur. because it is produced irpm a starting material containing sulphur, such as crude oil which contains sulphur.

Another object of my invention is to purify a "distillate containing this high percentage of sulphur so that it is rendered commercial by reducing the sulphur content to or below 0.10 percent which is the limit set up by the United States government.

Other objects of my invention will be set forth in the following description and diagrammatic drawing which illustrate a-preferred embodiment thereof, it being understood that the above general statement of the objects of my invention is intended merely to generally explain the same and not to limit it in any manner.

Heretofore, in order to reduce the sulphur content of an oil, it has been common practice to treat the oil with sulphuric acid and alkaline 0 solutions of lead oxide or to produce other chemical reactions for removing the sulphur. Such processes are wasteful and in addition, produce chemical changes in the gasoline or the like which renders the gasoline less valuable, since 5 one of the requirements for gasoline is that it shall produce minimum knocking when utilized in an internal combustionengine.

According to my invention, sulphur-containing substances can be treated to sufliciently reorganic sulphides and hydrogen sulphide is also produced. The hydrogen sulphide can be removed much more readily than the mercaptans so that the sulphur content of the starting material can be readily reduced fifty percent.

In the diagrammatic drawing forming part 35 of this specification, l indicates a heating furnace or chamber into which a starting material, is forced by a pump 3. The heating chamber or furnace 1 communicates with the reaction chamber 2 which for convenience may be designated as the catalytic tower, in which is placed a mass of silica gel or other suitable siliceous material. While I prefer to use siliceous material in the catalytic chamber, I do not restrict myself to the use of silica gel as I could also use siliceous materi- 7 al in the form of coarse particles of silica rock. This is prepared by grinding silica rock, rejecting the fine powder and using the coarser particles such as are equivalent to' No. 10 mesh. The silica gel is used in the form of a coherent mass, like a filter bed. This is so porous that the vapors pass through it readily. Y

The starting material, such as oil, which is forced into the heating chamber 1, is raised to 105., a temperature of 780-820 F. as I have found that within thi range of temperature, there is a minimum formation of deposits on the silica gel or other material which .is utilized. This'is an important feature of my invention because the; 1

' sure which isslightly above the atmospheric pressure, or at a pressure which is not sufiicient to cause the vapor to condense. The heated vapor passes through the catalytic mass in chamber 2, so that the sulphur compounds are transformed into organic sulphides and hydrogen sulphide.

The mixture of purified vapor and of hydrogen sulphide passes through a condenser in a coil or coils which is cooled by a counterfiow of water so that the hydrocarbon vapors condense and absorb large quantities of the hydrogen sulphide. The hydrogen sulphide can be removed by Waterwashing in a counter-current scrubber system of the usual type and the purified gasoline or other oil is thus rendered non-corrosive to copper and other metals. In addition to the water scrubbing, an alkali wash with lye can also be employed to meet the requirements of the doctor test.

The distillate so produced is usually water white and neutral and it is free from corrosive sulphur compounds and from the very objectionable odor of the raw material.

It is clear that my method can be directly applied'to a supply of raw vapor coming from a fractionating tower which is connected to a shell or still of any type. If my method is used to treat the material from a pipe still or a cracking still, it is only necessary to heat the vapors to an effective temperature.

Since silica gel has different properties according to the method of preparation thereof, I prefer to use the silica gel sold under the trade name fDucil, because this has a very large effective area of contact and it is stable at the temperatures employed.

While I do not wish to commit myself to any definite theory of operation in View of the fact that chemists are not agreed as to whether reactions of this type are produced by the adsorbent properties of the contact mass utilized, or whether said contact mass has a so-called specific catalytic action, I believe that the reaction produced is as follows: If silica particles are maintained in a current of air under suitable conditions, such as freedom from dust, it can be noticed that the surface appearance of the silica particles changes as though a surface oxidation had been produced. No chemical test sufficiently delicate has yet been devised whereby this surface film or layer has been isolated or analyzed. 'Since oxygen and sulphur have a great many similar chemical reactions, I consider that the sulphur forms an unstable compound with the silicon which is immediately decomposed.

Furthermore, it is known that silicon sulphide isv obtained by heating amorphous silicon with sulphur and that this is decomposed by water to form hydrogen sulphide and orthosilicic acid. Since" silica gel contains water in some form, I consider that something similar to said reaction occurs. However, I do not wish to limit myself to any particular method of producing the above mentioned reaction and likewise, my invention is suiiiciently broad to cover any method whereby the sulphur-containing impurities in a raw startingfmaterial are transformed into another sulphur-containing compound or'compounds which can be more readily removed than the original impurity. In particular, it is a great advantage of my method that no additional material must be added to the raw starting material, so that the raw material can be directly treated as it comes from a still or the like, to transform the original sulphur-containing impurities to another sulphur-containing compound or compounds which can be more readily removed.

Hence, in the broader aspects of my invention, it is wholly immaterial whether the raw starting material is caused to contact with an adsorbent material, or with a material having a specific catalytic reaction in the sense that it produces an intermediate unstable compound, as I consider that the action of the siliceous material in proper form is to produce an intermediate sulphide of silicon which is broken down to form hydrogen sulphide.

Generally speaking, while I have shown a preferred embodiment of my invention, it is clear that numerous changes and omissions could be made without departing from its spirit. For example, best commercial practice would make it desirable to remove all of the gaseous compound (hydrogen sulphide), which is produced from the sulphur originally present in the starting material. I do not wish to be limited to a complete elimination of hydrogen sulphide as my invention is broad enough to cover a sunicient removal of the original sulphur impurity to make the treated material commercially available. Hence, when I specify the purification of the starting material, either in the description or the claims, it is to be iuiderstood that I intend to cover a suificient lowering of the sulphur content to render a material which is commercially unavailable, fit for commercial use. Likewise, it must be realized that working conditions may be changed dependent upon the particular raw material which is treated and that additions and variations may be required depending upon particular raw material which is being utilized. I have found the above treatment effective when used with oil or distillates secured from oil fields in Lima Ohio, Venezuela and Canada. Likewise, the process applies to oils secured from coal tar, lignite and shale.

It will be noted that the material which is to be partially or wholly purified is subjected to the action of the silica gel while the material is in vapor form, and that it is not necessary to add hydrogen or other substances to the material, in order to accomplish either the partial or the complete removal of the sulphur.

I claim:

1. In the art of purifying the petroleum distillate which can be vaporized at a temperature of 780 F. and which contains an organic sulphide, those steps which consist in subjecting the petroleum distillate in vapor form to the action of contact material which consists substantially of silica gel and without the addition of any substantial quantity of other substances adapted to react with the petroleum distillate while it is so subjected to the action of said contact material, so that the purification is produced substantially by the decomposition of the sulphide to form hydrogen sulphide, the reaction temperature being maintained sufficiently high so as to cause the organic sulphide to decompose in order to form hydrogen sulphide and condensing the petroleum distillate vapor after it has been subjected to the action of said contact material, while preventing any substantial contact between the silica gel and the petroleum distillate save when the petroleum distillate is in the form of a vapor.

2. A method of purifying a petroleum distillate which can be vaporized at a temperature of 780 F. and which contains an organic sulphide which consists in subjecting the petroleum distillate in vapor form to the action of contact material which consists substantially of silica gel, while maintaining the temperature of the petroleum distillate vapor below the point at which any substantial objectionable deposits are formed on the silica gel, the reaction temperature being maintained sufiiciently high so as to cause the organic sulphide to decompose in order to form hydrogen sulphide and condensing the petroleum distillate vapor after it has been subjected to the action of said contact material, while preventing any substantial contact between the silica gel and the petroleum distillate save when the petroleum distillate is in the form of a vapor, and then at least partially removing the hydrogen sulphide which is formed by said treatment from the petroleum distillate.

3. In the art of treating a petroleum distillate, which can be vaporized at a temperature of 780 F., those steps which consist in subjecting the oil in vapor form to the action of silica gel at a temperature substantially from '730 820 F., and condensing the oil after it has been subjected to such action, while preventing any substantial contact between the silica gel and the oil save when the oil is in the form of a vapor.

4. In the art of purifying a petroleum distillate containing an organic sulphide and which can be vaporized at a temperature of 780 F. those steps which consist in subjecting the petroleum distillate in vapor form to the action of contact material which consists substantially of silica gel and without the addition of any substantial quantity of other substances adapted to react with the petroleum distillate while it is so subjected to the action of said contact material, so that the purification is produced substantially by the decomposition of the sulphide to form hydrogen sulphide, the petroleum distillate in vapor form being maintained at a temperature sufiiciently high to produce decomposition and condensing the petroleum distillate vapor after it has been subjected to the action of said contact material, while preventing any substantial contact between the silica gel and the petroleum distillate save when the oil is in the form of a vapor, and while preventing any substantial chemical reaction save the decomposition of the sulphide.

5. A method of purifying a petroleum distillate containing an organic sulphide and which can be vaporized at a temperature of 780 F., which consists in subjecting the petroleum distillate in vapor form to the action of contact material which consists substantially of silica gel, while maintaining the temperature of the petroleum distillate vapor below the point at which any substantial objectionable deposits are formed on the silica gel, and condensing the petroleum distillate vapor after it has been subjected to the action of said contact material, while preventing any substantial contact between the silica gel and the petroleum distillate save when the oil is in the form of a vapor, and then at least partially removing the hydrogen sulphide which is formed by said treatment from the petroleum distillate, and while preventing any substantial chemical reaction save the decomposition of the sulphide, the temperature of the oil in vapor form being sufficiently high to cause the organic sulphide to decompose in order to form the hydrogen sulphide.

6. A method of treating a petroleum distillate which contains an organic sulphide and which can be vaporized at a temperature of 780 E, which consists in subjecting it in vapor form to the action of silica gel contact material, and condensing the petroleum distillate vapor after it has been subjected to said action, while preventing any substantial contact between the silica gel and the petroleum distillate in liquid form, the reaction being carried on without any substantial hydrogenation of the petroleum distillate.

'7. A method of treating petroleum distillate which can be vaporized at a temperature of 780 F., and which contains an organic sulphide, which consists in subjecting the petroleum distillate in vapor form to the action of silica gel contact material, said petroleum distillate vapor being then maintained at a sufiiciently high temperature to cause said organic sulphide to decompose in order to form hydrogen sulphide, and condensing the petroleum distillate vapor after it has been subjected to said action, while preventing any substantial contact between the silica gel and the petroleum distillate, save when the petroleum distillate is in vapor form.

HARRY WHITAKER. 

